Mof-derived porous carbon materials for carbon dioxide capture

ABSTRACT

The MOF-derived porous carbon materials for carbon dioxide capture, more specifically comprising a method for preparing thereof and the porous carbon materials for the purpose of CO 2  absorbent, wherein the porous carbon materials from zinc-containing three MOFs (MOF-5, MOF-177, and bioMOF-100) are synthesized by a simple pyrolysis and thereby the porous carbon materials have promising CO 2  capture capacity and selectivity compared to parent of MOFs prior to pyrolysis, particularly, the CO 2  capture capacity of the porous carbon materials is maintained under humid condition.

FIELD OF THE INVENTION

The present invention relates to MOF-derived porous carbon materials for carbon dioxide capture, more specifically comprising a method for preparing thereof and the porous carbon materials for the purpose of CO₂ absorbent, wherein the porous carbon materials from zinc-containing three MOFs (MOF-5, MOF-177, and bioMOF-100) are synthesized by a simple pyrolysis and thereby the porous carbon materials have promising CO₂ capture capacity and selectivity compared to parent of MOFs prior to pyrolysis, particularly, the CO₂ capture capacity of the porous carbon materials is maintained under humid condition.

BACKGROUND OF THE INVENTION

Continuous carbon dioxide (CO₂) emission from anthropogenic sources causes severe environmental issues such as global warming. The largest CO₂-emitting industrial sources are coal-fired power plants, in which post-combustion capture is often utilized to remove CO₂ from exhaust gas generated from combustion of fossil fuels. Flue gas from power plants is composed of carbon dioxide (˜15-16%), water vapor (˜5-7%) and nitrogen (˜70-75%) at ˜1 bar.

In order to separate and capture CO₂ from flue gas emissions at a power plant, monoethanol amine (MEA)-based aqueous solution is conventionally employed.

However, this wet-process requires a high-energy cost to regenerate absorbents because of not only an inherent high heat capacity of water in MEA solution but also chemisorption of CO₂ on MEA. Approximately 30% of energy produced from the power plants is usually wasted to regenerate the aqueous MEA

Solution

Moreover, volatility of MEA solution at high temperature and its corrosive character limit a wide use of MEA as an adsorbent for large-scale CO₂ capture.

Porous solid materials, which have lower heat capacity, have been emerging as a potential adsorbent for CO₂ capture application. Specifically, materials including zeolites, carbon materials, porous organic polymers (POPs) and amine-grafted silicas have been studied so far.

Among the various porous solids, metal-organic frameworks (MOFs), which are assembled by a coordination bond between a rigid organic ligand and diverse metal ions or metal clusters, have emerged as an outstanding adsorbent for CO₂ capture because of their enormous surface area and finely tunable surface functionality.

The study from Matzger and coworkers has demonstrated MOFs' excellent promising potential as CO₂ adsorbent, showing that [Mg₂ (DOBDC)] (DOBDC=2,5-dioxido-1,4-benzenedicarboxylate) exhibited a remarkable CO₂ uptake capacity (27.5 wt %) at 298 K and 1 bar.

However, most MOFs show instability toward moisture unfortunately, and it is one of the greatest challenges for establishing CO₂ capture from the flue gas containing water vapor.

Particularly, MOF-5 and MOF-177, composed of oxo-zinc secondary building unit and carboxylate linker, are known for their extreme instability upon exposure to moisture. In fact, MOF-5 showed a significant decrease of dynamic CO₂ adsorption capacity under humid condition (RH=65%) during three consecutive cycles.

Porous carbon materials and metal or metal oxide-carbon (M{circle around (a)}C or MO{circle around (a)}C) composites which are derived from MOFs have been used widely as platforms for green energy applications such as fuel cells, Li-ion batteries, supercapacitors and solar cells. In general, a simple pyrolysis of pristine MOF precursors affords these materials, and MOF-derived porous carbon materials are moisture stable due to the inherent hydrophobic property of porous carbon.

While numerous examples exist for electrochemical applications with these materials, to the best our knowledge, there are relatively few examples reported for capturing CO₂ with MOF-derived porous carbon materials, and most of the studies are limited to ZIF-8 (ZIF: zeolitic imidazolate frameworks) which is constructed from imidazolates and zinc(II) ions.

Besides, CO₂ adsorption study of these materials under humid conditions has not been reported yet.

PRIOR ARTS Other Publications

(Publication 1) S. R. Caskey, A. G. Wong-Foy and A. J. Matzger, J. Am. Chem. Soc., 2008, 130, 10890-10871.

DETAILED DESCRIPTION OF THE INVENTION Problems to be Solved

For the purpose of satisfying the needs described above, the present invention provides porous carbon materials from zinc-containing MOFs (MOF-5, MOF-177, and bioMOF-100), a method for preparing thereof by a simple pyrolysis, and the porous carbon materials for the purpose of CO₂ absorbent.

The inventor identified a structure, porous property, surface area, CO₂ capture capacity and selectivity of CO₂ capture in three types of porous carbon materials (M5-1000, M177-1000 and B100-1000) from metal-organic frameworks (MOFs), which are synthesized by a simple pyrolysis. Additionally, the present inventor demonstrated that CO₂ capture capacity is maintained under humid conditions through dynamic breakthrough experiments.

Solution

For solving the above problems, the present invention provides porous carbon materials from metal-organic framework (MOF),

wherein the porous carbon materials are synthesized by pyrolysis of a zinc-containing metal-organic framework, and the zinc-containing metal-organic framework is one selected from a group consisting of MOF-5, MOF-177 and bioMOF-100;

the pyrolysis removes all of zinc, thereby forming metal-free porous carbon structure; and

the porous carbon materials are used for carbon dioxide (CO₂) capture (Image 1).

The three types of MOF have high surface areas over 3000 m² g⁻² as well as thermally removable zinc elements, and thus can be a desirable precursor for forming porous carbon materials.

Additionally, bioMOF-100 contains nitrogens in adeninate ligands, and thus CO₂ capture capacity of nitrogen-doped porous carbon material was tested in the present invention.

FIG. 9 is a schematic illustration of the preparation of porous carbon materials and their selective adsorption of CO₂.

In the present invention, pore size in the zinc-containing metal-organic framework (MOF) can be shrunken by pyrolysis and thus a suitable confined-space for CO₂ uptake can be provided.

Moreover, the pyrolysis can make the porous carbon materials in the present invention have amorphous property.

More specifically, the porous carbon materials in the present invention can have smaller micropore sizes compared to those of parent MOFs, and the pore size can be 4 Å to 8 Å.

When a MOF precursor, MOF-5 as zinc-containing metal-organic framework (MOF) is used, BET specific surface area of porous carbon materials (M5-1000) having porous carbon structure formed by pyrolysis of the MOF-5 may be 1978 m² g⁻¹, and CO₂ capture capacity of the porous carbon materials may be 0.81 mmol g⁻¹ under 298K and 0.15 bar, and CO₂ capture capacity of the porous carbon materials may be 3.13 mmol g⁻¹ under 298K and 1 bar.

Further, when MOF-177 as zinc-containing metal-organic framework (MOF) is used, BET specific surface area of the porous carbon materials (M177-1000) having porous carbon structure formed by pyrolysis of the MOF-177 may be 1039 m² g⁻¹, and CO₂ capture capacity of the porous carbon materials may be 0.97 mmol g⁻¹ under 298K and 0.15 bar, and CO₂ capture capacity of the porous carbon materials may be 3.30 mmol g⁻¹ under 298K and 1 bar.

Moreover, when bioMOF-100 as zinc-containing metal-organic framework (MOF) is used, BET specific surface area of the porous carbon materials (B100-1000) having porous carbon structure formed by pyrolysis of the bioMOF-100 may be 958 m² g⁻¹, and CO₂ capture capacity of the porous carbon materials may be 0.98 mmol g⁻¹ under 298K and 0.15 bar, and CO₂ capture capacity of the porous carbon materials may be 2.69 mmol g⁻¹ under 298K and 1 bar.

Among porous carbon materials in the present invention, N-doped porous carbon, B100-1000, may exhibit a better adsorption capacity and selectivity for CO₂ than other materials in the low pressure region, which can be caused by the improved CO₂ capture capacity at the existence of Lewis basic nitrogen.

Particularly, bioMOF-100 may maintain CO₂ capture capacity under humid condition, and thus be used suitably for CO₂ capture from flue gas including water vapor.

To be more specific, B100-1000 may separate CO₂ from CO₂/N₂ gas mixture under 50% of relative humidity (RH).

In another aspect of the present invention, a method for producing porous carbon materials from zinc-containing metal-organic framework (MOF) is provided, comprising:

-   S1) preparing MOF-5, MOF-177, or bioMOF-100 as metal-organic     frameworks; and -   S2) removing zinc by pyrolysis of the zinc-containing metal-organic     framework, thereby forming metal-free porous carbon structure; -   wherein the produced porous carbon materials may be used for CO₂     capture.

The pyrolysis may be performed at 1000° C. for 6 hours.

Specifically, the pyrolysis may be performed at 1000° C. for 6 hours after the zinc-containing metal-organic framework is heated with rate of 5° C./min until the temperature reaches 1000° C. under argon (Ar) atmosphere.

Effect of the Invention

Porous carbon materials from metal-organic framework in the present invention have an increased amount of CO₂ capture, an improved CO₂ capture capacity and selectivity more than a parent metal-organic framework.

Especially, porous carbon materials from metal-organic framework in the present invention maintains an excellent CO₂ capture capacity under humid condition, and thus can be applied properly to flue gas including water vapor from a thermoelectric power plant.

Additionally, porous carbon materials from metal-organic framework in the present invention can be synthesized by a simple pyrolysis of a MOF precursor.

Further, porous carbon materials from metal-organic framework in the present invention can be regenerated under warm condition after used for CO₂ capture, and thus be reused consequently.

The present invention can be used for producing a porous carbon absorbent using zinc (and nitrogen)-containing MOF precursors other than MOF-5, MOF-177 and bioMOF-100.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a graph (a) which is a graphic representation of powder X-ray diffraction (PXRD) patterns of the porous carbon materials, and a graph (b) which is a graphic representation of Raman spectra of M5-1000, M177-1000, and B100-1000.

FIG. 2 depicts Scanning electron microscopy (SEM) images of (a) MOF-5, (b) M5-1000, (c) MOF-177, (d) M177-1000, (e) bioMOF-100 and (f) B100-1000.

FIG. 3 shows a graph (a) which is a graphic representation of N₂ adsorption-desorption isotherms of the porous carbon materials, and graphs 3(b)-(d) which are graphic representations of H-K pore-size distributions of M5-1000, M177-1000, B100-1000 and their pristine counterparts, respectively.

FIG. 4 is a graphic representation of DFT pore size distributions of the porous carbon materials.

FIG. 5 shows a graph (a) which is a graphic representation of CO₂ adsorption isotherms of the pyrolyzed samples and parent MOFs at 298 K, a graph (b) which is a graphic representation of Isosteric heats of adsorption (Q_(st)) of M5-1000, M177-1000, and B100-1000 for CO₂, and a graph (c) which is a graphic representation of CO₂/N₂ selectivity of M5-1000, M177-1000, and B100-1000 obtained from IAST at 298 K.

FIG. 6 is a graphic representation of N 1s X-ray photoelectron spectroscopy (XPS) of B100-1000.

FIG. 7 is a graphic representation of CO₂/CH₄ selectivity (298K) of the porous carbon.

FIG. 8 shows a graph (a) which is a graphic representation of experimental breakthrough curves at three consecutive cycles for a packed-bed filled with B100-1000 with a step-input of a dry CO₂/N₂ mixture (CO₂: N₂=15:85, total flow rate=40 ml min⁻¹) at 303 K and 1 bar, and a graph (b) which is a graphic representation of breakthrough curves of CO₂/N₂ mixture (CO₂: N₂=15:85, total flow rate=40 ml min⁻¹) over B100-1000 at 303 K under dry and humid conditions (RH=50%).

FIG. 9 is a schematic illustration of the preparation of porous carbon materials and their selective adsorption of CO₂.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, the present invention will be described in details based on examples. However, the examples are only for helping understand the present invention and the present invention is not limited thereto.

Example 1 Synthesis of Porous Carbon Materials

MOF-5, MOF-177 and bioMOF-100 were synthesized by a process reported in “H. K. Chae, D. Y. Siberio-Perez, J. Kim, Y. Go, M. Eddaoudi, A. J. Matzger, M. O'Keeffe and O. M. Yaghi, Nature, 2004, 427, 523-527” and “J. An, O. K. Farha, J. T. Hupp, E. Pohl, J. I. Yeh and N. L. Rosi, Nat. Commun., 2012, 3, 604.”

A solution of adenine, biphenyldicarboxylic acid and zinc acetate dihydrate in N,N′-dimethylformamide (DMF) and methanol is heated in a capped glass vial for 24 h, and thus solvothermal reaction was proceeded. Consequently, colorless polyhedral block-like crystals of anionic bio-MOF-100 including ZABU building unit was yielded (*Zn₈ (ad)₄ (BPDC)₆O₂. 4Me₂NH₂, 49DMF, 31H₂O).

In order to obtain porous carbon materials, zinc-based MOFs were pyrolyzed at 1000° C. for 6 h under Ar atmosphere. During the pyrolysis step, low boiling zinc metal (b.p. 907° C.) was completely removed and metal-free carbon materials were afforded consequently. Hereafter resultant porous carbons were denoted as M5-1000, M177-1000, and B100-1000, respectively.

EXPERIMENTAL EXAMPLES (1) Phase Structure of Porous Carbon Materials

The phase structures of the porous carbon materials were studied via powder X-ray diffraction (PXRD) measurements (FIG. 1a ). As shown in FIG. 1a , the samples displayed two weak and broad peaks around at 23 and 44°, which were assigned to the carbon (002) and (100) or (101) plane, respectively. These results indicate that the carbonized MOFs have an amorphous nature. Additionally, complete removal of zinc metal was verified by observing the absence of other peaks in PXRD.

(2) Local Structure of Porous Carbon Materials

Local structure information of the porous carbon materials was investigated by Raman spectroscopy (FIG. 1b ). The pyrolyzed MOFs showed two distinct D and G bands centered at 1344 and 1587 cm⁻¹ respectively, resulting from the disordered carbon structures and the vibration mode for the movement of two carbon atoms in a single graphene sheet in the opposite direction. The intensity ratio of G band to D band (I_(G)/I_(D)) is related to a degree of graphitization in carbon materials. The I_(G)/I_(D) values were 0.96, 0.87, and 1.03 for M5-1000, M177-1000, and B100-1000, respectively, indicating that the local carbon structures consist of both graphene and disordered carbon. Almost featureless second-order bands (2D and G+D) were observed between 2700 and 3000 cm⁻¹ for all of the samples, suggesting a disordered carbon network as evidenced by the PXRD patterns.

(3) Morphology of Porous Carbon Materials

Scanning electron microscopy (SEM) images of the porous carbon materials are shown in FIG. 2. Interestingly, each morphology of the parent MOFs was found to be retained, even after heating at high temperature. This indicates that the carbon content of the MOFs is suitable for the formation of carbon materials and the MOF is a stable support for the synthesis of the porous carbon materials.

(4) Pore Structure and Surface Area of Porous Carbon Materials

Detailed information about pore structures and surface areas of the pyrolyzed carbon materials was investigated by N₂ adsorption-desorption isotherms at 77 K. As shown in FIG. 3a , the isotherms of M5-1000 and M177-1000 revealed type IV shape with noticeable hysteresis, whereas that of B100-1000 exhibited type I shape with insignificant hysteresis. BET surface areas from the N₂ isotherms are shown in TABLE 1.

TABLE 1 Zn/C ratio of parent MOFs, BET surface areas, and CO₂ uptake properties of the porous carbon materials BET surface area (m²g⁻¹) CO₂ uptake at 298K (mmolg⁻¹) Zn/C ration of Parent After Parent MOFs After pyrolysis Q_(st)CO₂ Selectivity Sample Parent MOFs MOFs Pyrolysis (1 bar) 0.15 bar 1 bar (kJmol⁻¹) (IAST) M5-1000 0.167 3031  1978 1.09 0.81 3.13 28.1-22.1 21.6-11.0 M177-1000 0.074 3337  1039 1.18 0.97 3.30 27.6-22.9 20.0-13.5 B100-1000 0.071 4300^(a) 958 1.02 0.98 2.69 33.9-31.8 46.7-15.9 ^(a)This value is obtained from ref. 18.

Surface areas of the porous carbon materials were linearly increased with increasing Zn contents of parent MOFs precursors (TABLE 1).

Higher Zn contents in MOF precursors lead to a formation of larger amounts of Zn nanoparticles in the carbon matrix during the pyrolysis step.

Given that an evaporation of these Zn nanoparticles from the carbon matrix is responsible for the formation of the porous carbon structures, the above linear relationship between Zn contents and surface area might result from the different ratio of Zn/C in the parent MOF.

The DFT pore size distributions is shown in FIG. 4. B100-1000 was micropore-dominant while M5-1000 and M177-1000 have significant amounts of mesopores as well as micropores.

The detailed micropore size analysis was investigated using Horvath-Kawazoe (HK) model (FIG. 3b-d ). Interestingly, the obtained carbon materials revealed smaller micropore sizes compared to those of parent MOFs. Pore size plays a key role in CO₂ capture performance, and narrow pores of ˜4 Å to ˜8 Å are particularly suitable for CO₂ adsorption due to the efficient overlap of attractive potential fields of opposite walls. Therefore, narrowing pore sizes by pyrolysis of Zn based MOFs might be a good strategy for CO₂ adsorption.

(5) CO₂ Capture Capacity of Porous Carbon Materials

In order to test the above strategy, the CO₂ adsorption isotherms of the porous carbon materials and their parent MOFs were measured up to 1 bar at 273 and 298 K (FIG. 5a ).

As expected, all carbon materials revealed superior CO₂ capacities compared to those of their parent MOFs (FIG. 5a , and TABLE 1).

Micropore size distributions of the carbon materials were also shrunk to 4-8 Å after pyrolysis, thus enhanced performances for capturing CO₂ are presumably attributed to the generation of confined narrow space.

The CO₂ uptake for M177-1000 reached 3.30 mmol g⁻¹ at 1 bar and 298 K which was higher than those of both M5-1000 (3.13 mmol g⁻¹) and B100-1000 (2.69 mmol g⁻¹).

Adsorption amounts of all carbon materials were not saturated at 1 bar, suggesting a higher adsorption capacity for CO₂ at high pressure.

Flue gas from the power plants possess ˜15% CO₂ at a total pressure of around 1 bar; consequently, the CO₂ uptake amount at 0.15 bar is an important index to evaluate adsorbents for realistic post-combustion capture of CO₂.

Uptake amount of M5-1000, M177-1000, and B100-1000 reached 0.81, 0.97, and 0.98 mmol g⁻¹, respectively, at 0.15 bar and 298 K. These values are comparable to those of representative inorganic carbon adsorbents.

Interestingly, the CO₂ uptake of B100-1000 at low pressures was slightly higher than those of M177-1000 and M5-1000, implying strong interactions between B100-1000 and adsorbed CO₂ molecules.

The isosteric heats of adsorption (Q_(st)) of M5-1000, M177-1000 and B100-1000 for CO₂ were calculated from the Clausius-Clapeyron equation to determine the adsorption affinity between the porous carbon materials and CO₂ molecules.

As depicted in FIG. 5b , B100-1000 showed higher Q_(st) for CO₂ (33.9 kJ mol⁻¹) at near zero coverage than those of M5-1000 (28.1 kJ mol⁻¹) and M177-1000 (27.6 kJ mol⁻¹).

Higher CO₂ uptake and Q_(st) of B100-1000 at low pressures might result from small amounts of Lewis basic nitrogen sites in the carbon matrix which had originated from adeninate ligands in bioMOF-100.

X-ray photoelectron spectroscopy (XPS) was carried out to verify the presence of Lewis basic nitrogen in the carbon surface (FIG. 6).

The atomic percentage of N in B100-1000 was 2.69%.

The high resolution N is spectrum of B100-1000 can be deconvoluted into three peaks corresponding to pyridinic N (398.5 eV), graphitic N (401.3 eV), and N-oxide (403.3 eV) respectively.

The presence of Lewis basic pyridinic N sites for CO₂ adsorption influence significantly on CO₂ capture. Therefore, the higher affinity of B100-1000 toward CO₂ in the low pressure region is attributed to the existence of Lewis basic nitrogen in the porous carbon surface.

(6) CO₂ Capture Selectivity of Porous Carbon Materials

Ideal adsorption solution theory (IAST) is normally conducted to predict the adsorptive behaviors of a two-component gas mixture from single-component isotherms.

The IAST adsorption selectivity for CO₂/N₂ at 298 K was calculated for 15/85 gas mixtures.

The experimental CO₂ and N₂ isotherms collected at 298 K for all carbon materials were fitted to the dual site Langmuir-Freundlich model. FIG. 5c and TABLE 1 show the IAST selectivity for CO₂/N₂ in the flue gas condition.

B100-1000 exhibited better performance for separating CO₂ from a gas mixture than other two carbon materials.

Selective adsorption of CO₂ from CO₂/CH₄ gas mixture is an important process in shale gas extraction.

Thus, the IAST adsorption selectivity for CO₂/CH₄ at 298 K was also calculated for 50/50 gas mixtures.

As depicted in FIG. 7, M177-1000 showed slightly higher selectivity toward CO₂ than other carbon materials.

However, selectivity of all porous carbons for CO₂/CH₄ are not greatly impressive, this might result from favorable interactions between the hydrophobic carbon surface and methane gas molecules.

(7) Dynamic Breakthrough Experiment

B100-1000 revealed superior CO₂ uptake and separation performance in the flue gas condition as described before.

Therefore, dynamic breakthrough experiments were performed to evaluate the potential of B100-1000 for the adsorptive separation of CO₂/N₂ mixtures.

FIG. 8 shows the breakthrough curves of CO₂ and N₂ upon separation of a CO₂/N₂ mixture (CO₂: N₂=15:85) on a column packed with B100-1000 pellets.

Nitrogen came out rapidly from the column, whereas carbon dioxide was strongly retained.

This clearly shows that B100-1000 can separate CO₂ and N₂ under dynamic flow conditions.

After performing a breakthrough experiment with a CO₂/N₂ mixture, the column was regenerated by purging it under a He flow of 40 ml min⁻¹ for 30 min without heating the column.

As shown in FIG. 8, essentially identical breakthrough curves were produced during the three consecutive cycles.

Such result was remarkable because the regeneration was performed under mild conditions.

In addition, since flue gases contained considerable amounts of water vapor, it was important to assess the performance of an adsorbent for CO₂/N₂ separation under humid conditions (RH=50%). As displayed in FIG. 8b , almost similar breakthrough curves were obtained even in humid conditions.

This indicates that B100-1000 adsorbent retains CO₂/N₂ separation ability well under humid conditions. As such, these results demonstrate the separation potential of B100-1000 for CO₂/N₂ mixtures under dynamic flow conditions in the presence of water vapor.

Review the Result

In the present invention, porous carbon materials (M5-1000, M177-1000, and B100-1000) were prepared by simple pyrolysis of pristine MOFs (MOF-5, MOF-177, and bioMOF-100).

The pyrolysis step led to the shrunken pore size of these materials and provided a suitable confined-space for CO₂ uptake. Consequently, all carbon materials revealed a remarkable enhancement of CO₂ uptake capacities compared to their parent MOFs.

Among the carbon materials, N-doped porous carbon, B100-1000, exhibited a better adsorption capacity and selectivity for CO₂ than other materials in the low pressure region, because the existence of the Lewis basic nitrogen was responsible for the improved CO₂ uptake.

Dynamic breakthrough experiments with B100-1000 showed that the B100-1000 can separate CO₂ and N₂ under dynamic flow conditions. Moreover, the separation ability of B100-1000 was retained even under humid condition.

MOF-derived porous carbons according to the present invention, which have narrow-sized micro-pores and Lewis basic sites, can be an excellent adsorbent for post combustion CO₂ capture process.

Further, it is possible that the present invention can be applied to a method for preparing porous carbon adsorbents using another zinc (and nitrogen)-containing MOFs other than MOF-5, MOF-177 and bioMOF-100 as precursors. 

What is claimed is:
 1. Porous carbon materials from a metal-organic framework (MOF), comprising: wherein the porous carbon materials are synthesized by pyrolysis of a zinc-containing metal-organic framework, and the zinc-containing metal-organic framework is one selected from a group consisting of MOF-5, MOF-177 and bioMOF-100; the pyrolysis removes all of zinc, thereby forming metal-free porous carbon structure; and the porous carbon materials are used for carbon dioxide (CO₂) capture.
 2. The porous carbon materials of the claim 1, comprising micropores smaller than pores of parent MOF wherein size of the mircopores is 4 Å˜8 Å.
 3. The porous carbon materials of the claim 1, having amorphous property.
 4. The porous carbon materials of the claim 1, wherein the zinc-containing metal-organic framework is MOF-5, and BET specific surface area of porous carbon materials having porous carbon structure formed by pyrolysis of the MOF-5 is 1978 m² g⁻¹, and CO₂ capture capacity of the porous carbon materials is 0.81 mmol g⁻¹ under 298 K and 0.15 bar, and CO₂ capture capacity of the porous carbon materials is 3.13 mmol g⁻¹ under 298 K and 1 bar.
 5. The porous carbon materials of the claim 1, wherein the zinc-containing metal-organic framework is MOF-177, and BET specific surface area of porous carbon materials having porous carbon structure formed by pyrolysis of the MOF-177 is 1039 m² g⁻¹, and CO₂ capture capacity of the porous carbon materials is 0.97 mmol g⁻¹ under 298 K and 0.15 bar, and CO₂ capture capacity of the porous carbon materials is 3.30 mmol g⁻¹ under 298 K and 1 bar.
 6. The porous carbon materials of the claim 1, wherein the zinc-containing metal-organic framework is bioMOF-100, and BET specific surface area of porous carbon materials having porous carbon structure formed by pyrolysis of the bioMOF-100 is 958 m² g⁻¹, and CO₂ capture capacity of the porous carbon materials is 0.98 mmol g⁻¹ under 298 K and 0.15 bar, and CO₂ capture capacity of the porous carbon materials is 2.69 mmol g⁻¹ under 298 K and 1 bar.
 7. The porous carbon materials of the claim 1, wherein the zinc-containing metal-organic framework is bioMOF-100, and porous carbon materials having porous carbon structure formed by pyrolysis of the bioMOF-100 maintain CO₂ capture capacity under humid condition.
 8. The porous carbon materials of the claim 7, wherein the porous carbon materials are used for CO₂ capture from flue gas including water vapor.
 9. The porous carbon materials of the claim 8, wherein the porous carbon materials separate CO₂ from CO₂/N₂ gas mixture under 50% of relative humidity (RH).
 10. A method for producing porous carbon materials from a zinc-containing metal-organic framework (MOF): S1) preparing MOF-5, MOF-177, or bioMOF-100 as a metal-organic framework; and S2) removing zinc by pyrolysis of the zinc-containing metal-organic framework, thereby forming metal-free porous carbon structure; wherein the produced porous carbon materials are used for CO₂ capture.
 11. The method of claim 10, wherein the pyrolysis is performed at 1000° C. for 6 hours.
 12. The method of claim 11, wherein the pyrolysis is performed at 1000° C. for 6 hours after the zinc-containing metal-organic framework is heated with rate of 5° C./min until the temperature reaches 1000° C. under argon (Ar) atmosphere. 